Background: Age-adjusted cancer mortality is 27% higher for Black Americans than for the general U.S. population, which may result from inappropriate use of cancer detection tests. Social support has been shown to affect adjustment to breast cancer and survival, but it has not been studied as a predictor of use of preventive health care services in the older population. Our hypothesis is that larger social networks are associated with greater utilization of cancer-screening tests in the older population. Purpose: The objective of this study was to examine the relationship between social support and use of cancer-screening tests among older Black Americans. Methods: Data for this study were obtained from a 1986 baseline survey evaluation of a community intervention program to increase cancer awareness and a 1991 end-point survey of use of cancer detection tests. Our study sample consisted of 617 Black Americans aged 55 years or older who lived in San Francisco (Calif.), the control community, and in Oakland (Calif.), the target community for intervention. The survey included measures of 1) social network characteristics, as determined by a modified version of Berkman and Syme's Social Network Index; 2) demographic characteristics; and 3) use of six cancer-screening tests-mammography, occult blood stool examination, cervical smear, clinical breast examination, digital rectal examination, and sigmoidoscopy. Results: Multiple logistic regression analysis of the Social Network Index results indicated statistically significant positive associations of social support with the use of mammography and occult blood stool examination but not with the other cancer-screening tests. There were statistically significant associations between having HMO (Health Maintenance Organization) insurance and increased use of mammography and occult blood stool examination, compared with having Medi-Cal or other insurance. The interval between the surveys had a statistically significant positive association with use of mammography. These significant associations were not explained by differences in the other variables, which included health status, age, gender, education, type of health insurance, interval between the surveys, and a regular source of care. Conclusions: Social support seems to be associated with increased use of mammography and occult blood stool examinations among older Black Americans. Implications: Interventions designed to increase utilization of social networks may be an effective way to increase use of cancer screening, which may ultimately lead to reduced mortality from cancer. [J Natl Cancer Inst 85: 737–742, 1993]